Fuels can be defined as substances which undergo combustion in the presence of air to produce a large amount of heat that can be used economically for domestic and industrial purpose. e.g. wood, coal, kerosene, petrol, diesel, coal gas, producer gas, natural gas, LPG, water gas, etc.

Characteristics of a good fuel: -

1. High Calorific value
2. High efficiency
3. Moderate ignition temperature
4. Moderate velocity of combustion
5. Low moisture content
6. Low non-combustible matter content
7. Low cost & low storage cost
8. Should not pollute the atmosphere
9. Should not undergo spontaneous combustion 10 Easy to handle, store & transport